Author: Andrew Lowry
Andrew Lowry
Andrew Lowry, a corporate professional and Senior Editor at mahdi.cheraghchi.info, is engrossed in mathematics every minute of his free time. His interests are deeply rooted in theoretical computer science, coding theory, information theory, and cryptography; he approaches these subjects as someone who genuinely cannot stop thinking about them rather than as a casual observer. He is most likely reading a proof when he is not in a meeting.
In complexity theory, there is a specific type of result that quietly shows up, is courteously cited, and then sits inside the field like a tiny stone in a shoe. That is similar to the new lower bounds for MCSP against branching programs and one-tape Turing machines. They don’t claim to be innovations. They practically make an effort not to. Nevertheless, it’s difficult to ignore how the writers are getting very close to the brink of something much larger when reading the proofs. ItemDetailTopicOne-tape Turing machine and branching program lower bounds for the Minimum Circuit Size ProblemFieldComputational complexity theoryCentral problemMCSP[s(n)]…
In information theory, there is a specific type of unresolved issue that subtly refuses to go away. Among them is the binary deletion channel. Even though it’s one of the most basic objects you can think of—a stream of bits, each of which is dropped with a fixed probability d—we still don’t have a clear formula for its capacity over fifty years after Levenshtein first described it. That in and of itself says something. In less time, entire fields of communication theory have been developed and closed. FieldDetailsTopicCapacity Upper Bounds for Deletion-Type ChannelsField of StudyInformation Theory, Coding Theory, ProbabilityOriginating ConceptIntroduced…
Tuesday mornings in Simonyi 101 are particularly quiet. The listening silence of a room where forty or fifty people are making a great effort to follow a single line of reasoning on a whiteboard, rather than the dead silence of a library. For years, the Institute for Advanced Study’s Computer Science and Discrete Mathematics seminar has been held in this manner, week after week, with minimal fanfare and hardly any outward effort to attract attention. However, this room consistently appears when you consider the sources of the most intriguing concepts in theoretical computer science over the past ten years. Irit…
The majority of computer users are unaware of FOCS. They won’t be aware that every fall, a few hundred theoretical computer scientists congregate in a hotel ballroom in Berkeley or a university auditorium in Chicago to debate complexity classes and prove things that won’t be relevant for business for another twenty years, if at all. However, many of the things we take for granted today, such as the algorithms that shape search results and the cryptography that powers banking apps, can be traced back, either directly or indirectly, to papers that were presented at this conference. The FOCS Steering Committee…
The idea of eliminating randomness from a system that relies on it has an almost poetic quality. Mahdi Cheraghchi’s 2011 EPFL doctoral thesis, a 206-page document that has subtly grown to be one of the more cited works at the nexus of computational complexity and coding theory, has that peculiar, lovely tension. It will never be read by most people. However, the concepts it contains influence how contemporary communication systems are developed, evaluated, and trusted. Derandomization theory poses a seemingly straightforward question at its core. It turns out that randomness is very helpful in computer science; it can be used…
The Minimum Circuit Size Problem has an almost unyielding quality. Since the 1950s, it has been sitting in the back room of computational complexity, watched, prodded, and occasionally yelled at, but never quite cornered. The question itself seems surprisingly straightforward. Can you compute a Boolean function given its truth table using a circuit that is at most θ in size? That completes the puzzle. Nevertheless, decades later, neither the NP-hardness nor the ease of MCSP have been established. The July 2020 ACM Transactions on Computation Theory paper by Cheraghchi, Kabanets, Lu, and Myrisiotis doesn’t claim to resolve that long-standing issue.…
On a gloomy November afternoon in Cambridge, stroll down Vassar Street and you’ll come across a structure that appears to have had a falling out with itself. The Stata Center by Frank Gehry folds, tilts, and leans in ways that buildings typically don’t. Travelers pause to take pictures of it. Pupils pass by without raising their heads. The Computer Science and Artificial Intelligence Laboratory at MIT, which has quietly shaped more of modern computing than most people realize, is located inside, somewhere between the slanted hallways and the whiteboards filled with equations. CSAIL doesn’t run advertisements. It’s not really necessary.…
One of those concepts that seems almost too sophisticated to be practical is secret sharing, which has been operating covertly for more than 40 years beneath the security architecture of government key-management systems, blockchains, and banks. The field has been following Adi Shamir’s shadow ever since he sketched it out in 1979 on what was, by all accounts, a fairly ordinary afternoon. Reading the most recent literature gives the impression that researchers are still working to complete a sentence he began. Pasin Manurangsi, Akshayaram Srinivasan, and Prashant Nalini Vasudevan’s paper on robust secret sharing against rushing adversaries, which appeared on…
One type of academic paper doesn’t shout. Arriving on arXiv on a Thursday night, it undergoes a quiet revision eleven days later. Over the course of years, it gradually transforms into something that other researchers cite without quite recalling when they first saw it. That includes the 2011 paper on submodular functions by Mahdi Cheraghchi, Adam Klivans, Pravesh Kothari, and Homin K. Lee. Although it is only a few pages long, the assertion it makes is the kind that subtly changes the way a field approaches a problem. When the formalism is removed, the argument becomes nearly unyielding in its…
A certain type of paper gradually permeates an entire field but doesn’t make headlines when it first appears. Among them is the paper by Cheraghchi-Indyk on the sparse Walsh-Hadamard transform. It first surfaced on arXiv in late April 2015. Like most theoretical computer science papers, it languished there for a while before making its way into ACM Transactions on Algorithms two years later. It’s difficult to ignore the fact that it has continued to receive citations over the years, including a new round in 2025 from venues related to information theory and cryptography. The stakes are strangely intuitive, but the…